Why facebook is hacked when using on someone else` computer?

Using facebook,twitter or any other website that requires log-in and password on someone else` computer can result in HACKING of your account because of a software called keylogger/key-recorder.The main function of kelogger is to record and save every key you are pressing.So your password and email is hacked and your chat is also recorded.So always use your facebook on your own computer.